I know this is the folding forum, so the photo is not really pertinent. But sometimes having a big powerbank is not going to help if you can't charge it up, sometimes I travel where there are no places to plug in. And then a dynohub is the best option.

When I took the photo, I had not seen a place to plug in a charger for five days and I had several more days to go before I saw another place to plug in. I think I went for almost two weeks between places to charge up on mains power.

But next month I am going on a trip, the longest that I expect to go without the ability to plug into a charger is about four days, I am bringing a bike without a dynohub and plenty of charged up AA batteries for my GPS. I probably will not have cell service for three of those days, so charging the phone won't be a concern. I will have enough spare camera batteries to last a week. My taillights and my headlamp (for my head in campsite) usually last over a week on freshly charged AAA batteries.

I almost exclusively use Eneloop or Ikea Ladda AA and AAA rechargeable batteries, except cameras and phone take Li Ion batteries.